1. Field of the Invention
The present invention relates to a receiver for FM multiplex broadcasting, and more particularly, to a multiplex broadcasting receiver for receiving digital data of program information, weather forecast information, and the like multiplexed with a radio broadcasting wave and transmitted from a broadcasting station, and displaying the received digital data.
2. Description of the Background Art
FM multiplex broadcasting is one broadcasting system that multiplexes signals utilizing a spectrum region of a high base band spectrum of FM stereo audio broadcasting to provide service utilizing characters and figures in addition to the existing stereo broadcasting. A plurality of display formats of the FM multiplex broadcasting program are defined. FIG. 32 shows the display formats for FM multiplexed broadcasting programs. Referring to FIG. 32, the current display formats include five types of formats, i.e. formats 0-3 and a free format. Each display format is identified by the data transmitted as display format data. For example, a display format data "0001" designates format 0, wherein the number of display characters of one page is 2.5 lines.times.15.5 characters, which is 60.times.248 dots when calculated as the number of dots corresponding to a standard character. Similarly, formats 1-3 and the free format are defined as shown in FIG. 32.
A structure of a program data header including the data of the above-described display format will be described hereinafter. FIG. 33 is a diagram showing a structure of a program data header. Referring to FIG. 33, an 8-bit information separation code is stored in data block DB (n). Data header parameter of 8 bits is stored in data block DB (n+1). These are data header identifiers.
A program number of 8 bits is stored in data block DB (n+2). Information of 2 bits related to content update and the total number of pages in 6 bits are stored in data block DB (n+3). A presentation function of 8 bits is stored in data block DB (n+4). Information type of 4 bits and display format of 4 bits is stored in data block DB (n+5). Each of these data is a data header data.
The program data header is formed as described above. Data of the display format of FIG. 32 is stored in the lower 4 bits of data block DB (n+5). Therefore, the display format of each program is defined by the contents of the program information transmitted from a broadcasting source.
As described above, the display format is defined according to the program data header of each program. In a conventional FM multiplex broadcasting receiver, display was carried out exactly according to the display format specified by the broadcasting station on the basis of a predefined display format. Furthermore, the character size (display frame) of the display characters is limited to one of a range of specified sizes (number of horizontal dots: fixed to 16 dots; number of vertical dots: 18-24 dots in the Japanese language, for example). In other words, one type of character size was employed according to the application and grade of the FM multiplex broadcasting receiver.
As described above, the amount of information that can be displayed on one screen differs according to the display format in FM multiplex broadcasting. An FM multiplex broadcasting receiver corresponding to the format having the greatest display capacity of one screen of FM multiplex broadcasting becomes the most convenient apparatus for the user since the greatest amount of the information can be displayed. With an FM multiplex broadcasting receiver for format 1, information of one page of formats 0 and 1 can be displayed in one screen. In the case of an FM multiplex broadcasting receiver for format 0, information of one page of a program of format 0 can be displayed on one screen, but one page of information of format 1 cannot be displayed at the same time on that one screen. Therefore, display was effected by dividing the screen into a plurality of subscreens by operation of scrolling or the like.
In an FM multiplex broadcasting receiver corresponding to a display format of the greatest display capacity of one screen, a display unit and a memory of great capacity are required, resulting in a very expensive apparatus. Commercially, the factor of cost is given priority over the above-described operability in current FM multiplex broadcasting receivers. Therefore, FM multiplex broadcasting receivers for format 0 that can be manufactured at low cost are the main stream in the market. Since the amount of information that can be displayed in one screen is small under format 0 (display of 2.5 lines and 15.5 characters), the content of each program is sub-divided into a plurality of pages. The user selects the sub-divided pages individually for display on the display screen. There was a problem that the operation thereof is tedious.
The display format of FM multiplex broadcasting has the display region on the display screen defined physically, i.e. the header display region and the main passage display region. Here, information displayed in the header display region is, for example, the name of the broadcasting station, the broadcasting frequency, the page number, and the program name corresponding to the display in the main passage, which are information supplementary to the main passage (the program contents selected by the user to be displayed). For example, in an FM multiplex broadcasting receiver corresponding to format 0, the header display region occupied 20% of the entire display region.
FIG. 34 shows a display region of format 0. Referring to FIG. 34, the upper portion of the display region includes a header display region of 0.5 lines in width, and a main passage display region of 2 lines in width thereunder. Information of the header is always displayed in the header display region even when that information is not required. Furthermore, since one of the defined sizes (16.times.18.about.24 dots: the horizontal 16 dots is fixed in the Japanese language, for example) is employed, the dimension of the display character is fixed to that of the FM multiplex broadcasting receiver. Thus, the user cannot change the display character dimension arbitrarily (magnify/reduce the text), and operation for omitting the header cannot be specified. There was a problem that the level of visual confirmation of the information displayed on the display screen, and operability of the apparatus is not acceptable.
The program includes a sequential complementary type attribute and storage information type attribute. A sequential complementary program has information displayed only at the time of reception. The received information does not have to be stored at the receiver side. For example, the name of the tune or the singer displayed in association with the broadcasting music corresponds to this type. In contrast, a storage information type program stores the received information at the receiver side and displays the stored information. By receiving and storing a plurality of pages of information such as news, the user can view the news while scrolling through the pages. The program received in format 0 includes some sequential complementary programs and a plurality of storage information programs.
At the FM multiplex broadcasting receiver side, a menu screen of program information transmitted from the broadcasting station side appears to display a selected program. In a display device that can display a plurality of pages on one screen, a plurality of pages are displayed with and without the header.
In such a display device in which a plurality of pages can be displayed, a header of the same contents will be repeatedly displayed to result in loss of the display region when the display includes the header. In the case of a display output without the header, there was a problem that the contents of the program of respective pages cannot be identified. Furthermore, the latest page cannot be identified when scrolling back to a page associated with a sequential complementary program. Furthermore, it was not possible to view the contents of another storage information program during the waiting period for reception of the updated page of the sequential complementary program.